Wafer defect detection methods and systems

ABSTRACT

A wafer detection method. A plurality of PSL particles are sprayed on a wafer. An inspection operation is implemented on the wafer to obtain location information corresponding to a plurality of defects on the wafer, each location information corresponding to the defects comprises an error value. An inspection operation implemented on the PSL particles to obtain location information corresponding to the PSL particles. Offset location information corresponding to each defect is calculated according to the location information corresponding to each PSL particle. The error values corresponding to each defect are corrected according to the offset location information corresponding to each defect.

BACKGROUND

The invention relates to defect detection methods, and moreparticularly, to discover defect locations by spraying locatingparticles on a wafer.

In semiconductor manufacturing, wafers are inspected to discover defectsusing inspection tools during etching, developing, deposition, and otherprocesses. As critical dimensions for semiconductor processes aregradually decreased and precision and accuracy for wafer inspection areprogressively increased. To confirm product quality, high resolutionoptical instruments for integrated circuit (IC) manufacture/design mustbe employed to implement inspection processes. These processes compriseinspection after etching (AEI), inspection after developing (ADI),quality assurance (QA), quality control (QC), and others.

Wafer inspection mainly locates defects on a chip. Conventional waferprobe tests comprise testing related electrical characteristics of allmemory cells (arrayed in a matrix) on a chip, displaying coordinates offailed memory cells in the form of fail bit mapping (FBM), according totest results, in a coordinate region defined by X and Y axes, andestimating failure reasons according to analyzed FBM types, such aspoint-fail, block-fail, or line-fail. Fail bit mapping is an abnormalanalysis method for semiconductor components, visualizing addresses ofabnormal memory cells for confirmations.

Additionally, conventional wafer inspection methods further inspectwafers using an optical microscope, a scanning electron microscope(SEM), or a transmission electron microscope (TEM). The describedmicroscopes are widely employed in wafer and mask inspection and furtheremployed in crystal liquid display (LCD), compact discs, hard discs, QCand process management applications, nanotechnology,micro-electro-mechanical systems, and others.

Current inspection methods, however, have reached a bottleneck, and areincapable of further re-detection when extremely small (less than 100nm) particles or defects on wafers are detected, particularly forunpatterned wafers. When extremely small (10 nm or less) particles ordefects are detected, unpatterned wafers are employed to improve yields.Tiny defects, however, affect critically, such that defect re-detectionis important. Additionally, different tool settings (alignmentcoordinates, for example) may reduce the success rate for re-detection.

Thus, an improved wafer defect detection method for extremely smallparticles or defects is desirable.

SUMMARY

Wafer defect detection methods are provided. In an embodiment of such amethod, multiple locating particles are sprayed on a wafer. Aninspection operation is implemented on the wafer to obtain locationinformation corresponding to a plurality of defects on the wafer. Eachlocation information corresponding to the defects comprises an errorvalue. An inspection operation is implemented on the locating particlesto obtain location information corresponding to the locating particles.Offset location information corresponding to each defect according tothe location information corresponding to each locating particle arecalculated. Error values corresponding to each defect according to theoffset location information corresponding to each defect are corrected.

Also disclosed are wafer defect detection systems. An embodiment of sucha system comprises a particle spraying unit, a defect detection unit, aparticle detection unit, and a particle re-detection unit. The particlespraying unit sprays a plurality of locating particles on a wafer.

The defect detection unit implements an inspection operation on thewafer to obtain location information corresponding to a plurality ofdefects on the wafer, each location information corresponding to thedefects comprises an error value. The particle detection unit implementsan inspection operation on the locating particles to obtain locationinformation corresponding to the locating particles. The particlere-detection unit calculates offset location information correspondingto each defect according to the location information corresponding toeach locating particle, and corrects error values corresponding to eachdefect according to the offset location information corresponding toeach defect.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the subsequentdetailed description and examples of embodiments thereof with referencemade to the accompanying drawings, wherein:

FIG. 1 is a flowchart of a conventional wafer defect detection method;

FIG. 2 is a flowchart of an embodiment of a wafer defect detectionmethod;

FIG. 3 is a schematic view of an embodiment of a wafer defect detectionsystem; and

FIG. 4 is a schematic view of an example of wafer defect detection.

DETAILED DESCRIPTION

The invention discloses a wafer defect detection method and system.

A wafer defect detection method of the invention detects, but is notlimited to, extremely small (less than 100 nm) particles or defects onwafers.

As described, conventional defect detection methods can detect greatersize particles or defects on wafers. FIG. 1 is a flowchart of aconventional wafer defect detection method. A wafer is scanned andinspected to obtain location information corresponding to particle ordefect size on the wafer (step S11). The wafer is further scanned andinspected to obtain more accurate location information corresponding tosmaller size of particles or defects on the wafer (step S12). Due tohardware limitations, smaller particles or defects on the wafer cannotbe accurately located within an error value range between 50 um˜200 um,thus repairs cannot be implemented.

A wafer defect detection method detects relative locations of tinyparticles or defects on a wafer using polystyrene latex (PSL) particles,thereby obtaining correct location information corresponding to the tinyparticles or defects.

FIG. 2 is a flowchart of an embodiment of a wafer defect detectionmethod.

A plurality of PSL particles, each between 0.3˜0.5 um, are sprayed on awafer (step S21). An inspection operation is implemented on the wafer toobtain location information corresponding to particles or defects on thewafer (step S22), each location information corresponding to theparticles or defects comprising an error value. Next, an inspectionoperation is implemented on the PSL particles to obtain locationinformation corresponding to the PSL particles (step S23).

The size of a PSL particle, between 0.3˜0.5 um, confirms to the hardwarelimitations of a tool, and is able to obtain more accurate locationinformation. When location information corresponding to the PSLparticles is obtained, offset location information corresponding to eachtiny (less than 100 nm) particle or defect is calculated according tothe location information corresponding to each PSL particle (step S24).The error values corresponding to each particle or defect are correctedaccording to the offset location information corresponding to eachparticle or defect to estimate real locations requiring implementationof a defect repair process (step S25).

FIG. 3 is a schematic view of an embodiment of a wafer defect detectionsystem.

A wafer defect detection system 300 of the invention comprises aparticle spraying unit 310, a defect detection unit 320, a particledetection unit 330, and a particle re-detection unit 340. Particlespraying unit 310 sprays a plurality of locating particles on a wafer.Defect detection unit 320 implements an inspection operation on thewafer to obtain location information corresponding to a plurality ofdefects on the wafer, each location information corresponding to theparticles or defects comprises an error value. Particle detection unit330 implements an inspection operation on the PSL particles to obtainlocation information corresponding to the PSL particles. Particlere-detection unit 340 calculates offset location informationcorresponding to each tiny (less than 100 nm) particle or defectaccording to the location information corresponding to each PSLparticle, and corrects error values corresponding to each particle ordefect according to the offset location information corresponding toeach particle or defect to estimate real locations for implementation ofa defect repair process accordingly.

The described method for calculating offset location informationcorresponding to each particle or defect can be achieved using, but isnot limited to, mathematical operations. Additionally, locatingparticles sprayed on a wafer can be, but are not limited to, PSLparticles, particles conforming to hardware limitations of a tool areapplicable.

FIG. 4 is a schematic view of an example of a wafer defect detection.

Based on the described detection method and system, an example isillustrated. Referring to FIG. 4, PSL particles are sprayed on a wafer(step S21) and the wafer is scanned and inspected to obtain locationinformation of defects D₁′˜D₅′, comprising D₁′ (3, 3), D₂′ (3, 8), D₃′(8, 3), D₄′ (13, 8), and D₅′ (15, 3). Location information of realdefects D₁˜D₅ comprises D₁(2,2), D₂(4,6), D₃(10,5), D₄(12,9), andD₅(13,2). Real defects D₁˜D₅ are tiny and correct locations cannot bedetected, such that coordinates of divergent defects D₁′˜D₅′ aredetected. An error value is added to each coordinate of defects D₁˜D₅equal to each coordinate of defects D₁′˜D₅′. In this embodiment, tinydefects (less than 100 nm) are given as an example, other defects may bedetected using general detection methods are not described forsimplificity.

Next, sprayed PSL particles P₁˜P₅ are scanned and inspected, thusobtaining coordinates thereof, comprising P₁ (2,2), P₂(4,6), P₃(10,5),P₄(12,9), and P₅(13,2) (step S23). Offset location informationcorresponding to defects D₁˜D₅ and defects D₁′˜D₅′ is calculatedaccording to the coordinates corresponding to PSL particles P₁˜P₅ (stepS24). Offset of PSL particle P₁, for example, relative to defects D₁ anddefects D₁′, respectively, is identical, but, relative to the X-axis andY-axis corresponding to defects D₁ and defects D₁′, respectively, isdifferent. Error values corresponding to defect D₁′˜D₅′ are correctedaccording to the offset corresponding to the defects P₁˜P₅ to estimatereal coordinates for implementation of a defect repair process (stepS25).

A wafer defect detection method of the invention detects relativelocations of defects and then corrects error values correspondingthereto using PSL particles, thus obtaining real locations to increaseinspection success rates.

Although the present invention has been described in terms of preferredembodiment, it is not intended to limit the invention thereto. Thoseskilled in the technology can still make various alterations andmodifications without departing from the scope and spirit of thisinvention. Therefore, the scope of the present invention shall bedefined and protected by the following claims and their equivalents.

1. A wafer defect detection method, comprising: spraying a plurality oflocating particles on a wafer; implementing an inspection operation onthe wafer to obtain location information corresponding to a plurality ofdefects on the wafer, wherein each location information corresponding tothe defects comprises an error value; implementing an inspectionoperation on the locating particles to obtain location informationcorresponding to the locating particles; calculating offset locationinformation corresponding to each defect according to the locationinformation corresponding to each locating particle; and correctingerror values corresponding to each defect according to the offsetlocation information corresponding to each defect.
 2. The wafer defectdetection method as claimed in claim 1, wherein the locating particlesare PSL particles.
 3. The wafer defect detection method as claimed inclaim 1, wherein the size of each defect size is less than 100 nm.
 4. Awafer defect detection method, comprising: spraying a plurality oflocating particles on a wafer; implementing an inspection operation onthe wafer to obtain location information corresponding to a plurality ofdefects on the wafer, wherein each location information corresponding tothe defects comprises an error value; implementing an inspectionoperation on the locating particles to obtain location informationcorresponding to the locating particles; calculating offset locationinformation corresponding to error defect location and real defectlocation information relating to each defect according to the locationinformation corresponding to each locating particle; and correctingerror values corresponding to each defect according to the offsetlocation information.
 5. The wafer defect detection method as claimed inclaim 4, wherein the locating particles are PSL particles.
 6. The waferdefect detection method as claimed in claim 4, wherein the size of eachdefect is less than 100 nm.
 7. A wafer defect detection system,comprising: a particle spraying unit, spraying a plurality of locatingparticles on a wafer; a defect detection unit, coupled to the particlespraying unit, implementing an inspection operation on the wafer toobtain location information corresponding to a plurality of defects onthe wafer, wherein each location information corresponding to thedefects comprises an error value; a particle detection unit, coupled tothe defect detection unit, implementing an inspection operation on thelocating particles to obtain location information corresponding to thelocating particles; and a particle re-detection unit, coupled to theparticle detection unit, calculating offset location informationcorresponding to each defect according to the location informationcorresponding to each locating particle, and correcting error valuescorresponding to each defect according to the offset locationinformation corresponding to each defect.
 8. The wafer defect detectionsystem as claimed in claim 7, wherein the locating particles are PSLparticles.
 9. The wafer defect detection system as claimed in claim 7,wherein the size of each defect is less than 100 nm.